This invention relates to the treatment of Epstein-Barr virus (EBV) infection. More particularly, this invention relates to antisense oligonucleotides complementary to portions of the viral mRNA useful in inhibiting Epstein-Barr virus replication.
Epstein-Barr virus (EBV) is a human herpesvirus having a double-stranded DNA genome. It is a B lymphotrophic virus which is worldwide in distribution. Primary infection with EBV during childhood is usually subclinical. Between 25 and 70 percent of adolescents and adults who undergo a primary EBV infection develop the clinical syndrome of infectious mononucleosis. EBV is also associated with EBV syndrome, X-linked lymphoproliferative syndrome (XLP), and oral leucoplacia in AIDS patients, and with malignancies such as nasopharyngeal carcinoma, Burkitt's lymphoma, anaplastic nasopharyngeal carcinoma, Hodgkin's Disease, and hairy cell leukemia.
The diseases which have been attributed to EBV infection are diverse in part because, after entering the body via the oropharynx and entering an epithelial cell, the viral genome can replicate in alternative ways, leading to productive (lytic) or latent infection. EBV lyric infection causes the pathology related to the cytolysis of infected cells, often accompanied by the body's aberrant immunopathologic responses to viral antigens. In contrast, EBV latent infection occurs when the viral genome becomes fixed in epithelial or lymphoid cells as an episome, rather than in a viral particle. Episomes later appear in anaplastic nasopharyngeal carcinoma and in immortalized B-lymphocytes.
Productive EBV infection such as that associated with X-linked lymphoproliferative syndrome has been treated systematically with conventional anti-virus nucleoside analogs such as 9-(2-hydroxyethoxymethyl)guanine (acyclovir), 1-(2-fluoro-2-deoxy-B-D-arabinofuranosyl)-5-iodocytosine (FIAC), several E-5-(2-bromovinyl)-2'-deoxyuridine (BVdU)-containing compounds, and (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl) adenine ((S)-HPMPA) which traditionally have been used to inhibit the replication of other herpesviruses, as well as azido-thymidine (AZT) (reviewed in Pagano (in press). Pyrophosphate analogs, thymidine kinase analogs, and ribonucleoside reductase inhibitors have also been used. However, none of these drugs have been very effective in inhibiting EBV replication. In addition, the effect of these analogs is not limited to viral nucleotides, and thus unwanted side effects often present when they are used. Other therapies for EBV-associated disorders such as nasopharyngeal carcinoma have included surgery in combination with high doses of radiation. Radiation therapy has also been combined with chemotherapy in the treatment of EBV-related lymphomas, but often without much success. Thus, there remains a need for more effective treatment of EBV-related diseases which are specific for the virus, and which have few, if any, detrimental side-effects.
Recently, new chemotherapeutic agents have been developed which are capable of modulating cellular and foreign gene expression. These agents, called antisense oligonucleotides, bind to a target single-stranded nucleic acid molecules according to the Watson-Crick or the Hoogsteen rule of base pairing, and in doing so, disrupt the function of the target by one of several mechanisms: by preventing the binding of factors required for normal transcription, splicing, or translation; by triggering the enzymatic destruction of mRNA by RNase H, or by destroying the target via reactive groups attached directly to the antisense oligonucleotide.
Antisense oligodeoxynucleotides have been designed to specifically treat latent EBV infection by inhibiting the expression of the EBNA-1 gene of EBV (U.S. Patent No. 5,242,906). Antisense oligonucleotides have also been used to inhibit the expression of HIV-1, influenza, and other viruses (see, e.g., Agrawal et al., U.S. Patent No. 5,194,428; Pederson et al., U.S. Pat. Nos. 5,149,797; Agrawal (1992) Trends Biotechnol. 10:152-158; Agrawal et al. in Gene Regulation: Biology Antisense RNA and DNA (Erickson and Izant, eds.) Raven Press Ltd., New York (1992) pp. 273-283); Matsukura et al. in Prospects for Antisense Nucleic Acid Therapy of Cancer and AIDS, Wiley-Liss, Inc. (1992) pp. 159-178; and Agrawal (1991) in Prospector Antisense Nucleic Acid Therapy for Cancer and AIDS, (Wickstrom, ed.) Liss, New York, pp. 145-148).
A need for new strategies still remains for the treatment and prevention of EBV infections. In particular, compositions and therapeutic methods utilizing these compositions are desired which are effective and whose use are accompanied by little or no cellular toxicity.